Process for treating cellulosic materials



Patented May 20, 1952 UNITED STATES PATENT OFFICE rnocsss FOR TREATING CELLULOSIC MATERIALS Nicolas Drisch, Paris, and Andre Petiton, Saint- Just-Des-Marais, France, assignors, by mesne assignments, to Textile and Chemical Research Company Limited,'St. Peter Port, Guernsey, Channel Islands, a corporation ofv Great Britain No Drawing. Application March 20, 1950, Serial No. 150,798. In France April 5, 1949 Thus, resins,*'or products capable of conversion into" resins, have been added to the solution to be spun, and the yarns have also been treated with resins or products capable of conversion into resins. Products, have thus been obtained which have inter alia'a high elastic modulus and improved wetstrength and which are deformedto a smaller extent under load, while being less subject'to "swelling in aqueous media.

More particularly, U. S. Patent No. 2,495,232 dated January 24, 1950, describes a method of obtaining new cellulose derivatives by associating with the cellulose substances which contain free hydroxyl groups, monomeric polymethylol' phenols, and more particularly trimethylol phenols, and then subjecting the materials to heat treatment in the presence of an acid catalyst, which gives rise to the formation of bridge linkages of resinous groups between the cellulose chains.

According to French Patent No. 936,167 of May 25, 1943, there are added to the solutions to be, spun polymethylol phenols, in particular trimethylol phenols, which have undergone. a slight condensation (which lowers the solubility in aqueous media) but which still contain a considerable proportion of active methylol groups, and the solutions are then spun in the usual way. The yarns are treated by the known methods and are finally subjected to heat treatment in the presence of an acid catalyst.

Further, according to U. S. Patent No. 2,495,233, dated January 24, 1950, there are incorporated in the finished yarns monomeric polymethylol phenols, and more especially monomeric trimethylol phenols, and the yarns are then subjected to heat treatment in the presence of an acid catalyst. In both cases the addition of polymethylol phenols, sometimes in very small proportion, yields artificial yarns having in a high degree the particular characteristics hereinbefore mentioned, this being due to the extensive formation of resin bridge linkages between the cellulose chains. In some cases, where it is desired to obtain very pronounced effects, for example for the manufacture of bristles for 4 Claims. (or. 1854) 2 brushes, larger quantities of polymethylolphenols are employed.

Although the processes shown in the three above patents are of great importance and have enabled very useful products having remarkable properties to be produced, it has been found that the polymethylol phenols employed cause a cer-' tain yellowish coloration of the products. When the quantity of phenol incorporated is small, this coloration is not very. pronounced, but. when it' is desired to manufacture products having a high content of polymethylol phenol this coloration may become considerable, especially since it is frequently accentuated by bleaching. Thus. for example in the case of brushes, white bristles or at the most cream-colored bristles are preferred, and the products obtained, for example, by the process accordingto French Patent No. 936,167, are brownish.

Efiorts have already been made to remedy this. defect by employing polymethylol phenols obtained from substituted-phenols, and some progress has been made in this way, especially by.

employing trimethylol-p-isoamyl phenol, in accordance with United States Patent No. 2,495,239, dated January 24, 1950, but this, alternative has also been found unsatisfactory in the production of bristles.

The essential basis of the aforesaid processes is the formation of a substance resulting from the association of cellulose with a resinous substance. This association is obtained with the aid of groups of the resinous substance which are capable of reacting with the cellulose during, the subsequent condensing operation. It is therefore necessary to use a combination capable of increasing its molecular size by internal condensation while reacting with the cellulose. that it is possible to arrive at the same result by combining the cellulose, not with substances of low molecular weight which are capable of subsequent condensation, but with high polymers which are already condensed. In the latter case, the high polymers have. not sufficient reactivity to become associated with the active groups of the cellulose. .Hence it is necessary to employ an agent able to combine simultaneously with the hydroxyl groups of the cellulose and with the residual reactive groups of the high polymer employed. i

The object of the present invention is toprovide complexes of this type by intimately incorporating in the cellulose, linear polyesters of the polyacid-polyalcohol type, in such a state of condensation that their molecular weight is -al- We have now found ready high, but that there remain sufflcient free acid groups to ensure their solubility in solutions, and suflicient free hydroxyl groups in the cellulosic material to enable them to react with the linking agent which will subsequently be employed. In order to ensure the formation of a stable complex between these resins and the cellulose, various linking reagents may be employed. However, the most convenient is formaldehyde, which reacts with the free hydroxyls of the cellulose and the linear polymer ester and forms stable methylene bridges.

It is known to incorporate in artificial yarns, partially condensed glycero-phthalic acid products, namely glycero-phthalic acid resols, and to effect further condensation on the fiber by heat treatment. However, products which are partially condensed do not react sufiiciently with the hydroxyl groups to give the desired effect.

Moreover, it has been proposed to add linear superpolyesters or superpolyamides to the cellulosic solutions to be spun, in order to obtain certain special delustering or tinting effects, but the said linear super-polyesters or superpolyamides cannot undergo any further condensation on the fiber without damaging the fiber. Moreover, they are not capable of reacting readily with the free hydroxyl groups of the cellulose and their solubility in dilute alcohol is generally very reduced, except in the case of certain interpolymers.

A further feature of the invention is the supplementary treatment of yarns containing soluble linear polyesters of aliphatic diacids and dialcohols or other polyalcohols, with formaldehyde by heating in the presence of an acid catalyst, for the purpose of polymerizing the said polyesters on the fiber. This treatment affords a verv substantial increase in the stability of the effects obtained especially with regard to the reduction of the swelling in aqueous media. Thus. the supplementary treatment renders the effect much more stable to washing.

It will be appreciated that the swelling referred to is the quantity of water retained by the dry cellulosic substance after steeping in water, followed by centrifuging for ten minutes in a laboratory hydro-extractor rotating at 3000 revolutions per minute and having a diameter of, for example, 25 cm.

It is known to reduce th swelling of cellulosic substances. and more especially of artificial cellulose yarns, by impregnating with formaldehyde and an acid catalyst, followed by drying and heat treatment. This process, commonly known as formalizing is not the subject of the invention. While it results in a lowering of the swellin and in increased wet strength, it most frenuently also results in a substantial degradation of the material, unless carried out under very precise conditions of acidity, time and temperature. The process according to the present in-, vention may comprise a supplementary treat- -ment of the yarn similar to formalizing, but

under greatly moderated operating conditions.

According to the present invention use is made more especially of those products of the partial linear condensation of adipic acid and of glycol or glycerin, which are still soluble in dilute caustic soda, for example at a concentration of 4% to The reagents are heated in equimolecular Quantities for two to six hours at 130 C. to 160 C. in an oil bath, the reaction being controlled by checking the acid number. The reaction is considered as terminated when to of the carboxyl groups of the adipic acid are esterified. The product of condensation thus obtained is soluble in 4% to 10% caustic soda and also in the usual viscose solutions. Preferably, it is incorporated in the viscose solution in the form of a concentrated solution in dilute caustic soda containing 40% to 50% of the product. However, for application to finished yarns, use may be made of aqueous dispersions containing wetting agents, or of organic solutions, for example alcohol solutions.

When the heat treatment is applied at a temperature not exceeding, preferably, 90 C. to yarns containing the linear ester of aliphatic diacids and of aliphatic dialcohols or other polyalcohols, in the presence of formaldehyde, a complex is formed with bridge linkages between cellulose chains, in which linear polyester radicals are probably connected by methylene bridges to two cellulose chains in accordance with the following formula:

(cellulose chain)-(--O-CH2) (OOCR-COO-R' (CH2-O) (cellulose chain) in which R is a, methylene chain, for example of 4 carbon atoms in the case of adipic acid, and R is a polyalcohol radical, for example in the case of glycerin, and n is a high number. In fact, this formula clearly explains the action of the formaldehyde acting in the form CH2( OH) 2, one hydroxyl group reacting with the cellulose hydroxyl group and the other with a terminal carboxyl group of the linear polyester. One feature of the present invention resides in the fact that very useful results are obtained with small quantities of formaldehyde, for example 10 g. per liter at the most, while the reaction of the formaldehyde with the cellulose on one Side and the linear polyester on the other, takes place at moderate temperature. The polyester acts to a certain extent as an acceptor of formaldehyde.

The invention will be more readil understood with reference to the following examples, which are not intended to constitute any limitations. Thus, although the invention is concerned more especially with the manufacture of artificial yarns such as rayon, artificial staple fiber, or bristles, it is also applicable to the manufacture of films. The invention is in no way limited to viscose filaments, but includes all artificial fila ments of cellulose or of cellulose derivatives still containing free hydroxyl groups. It covers in general all filaments containing chain molecules comprisinug active hydroxyl groups, such for example as yarns of polyvinyl alcohol or of partially saponified polyvinyl acetals. The appearance of the filaments may be modified, for example by suitable de-lustering agents, b any known method. Coloring agents may also be incorporated in the filaments by adding to the solutions to be spun coloring agents suitable for dyeing in the mass. The white color of the filainents facilitates the production of bright pure ones.

Example I To l0 liters of a viscose containing 6% of caustic soda and 9% of cellulose are added 20 cc. of a 50% solution, in 6% caustic soda, of the product of condensation of adipic acid and glycerm prepared in the manner hereinbefore described. This viscose is then cured to a salt point of 6.0 and is spun through a spinneret having 2500 holes of a diameter of 0.08 mm. in a bath containing 120 g. of sulphuric acid, 250 g. of sodium sulphate and 15 g. of zinc sulphate per liter, at a temperature of 48 C'. After travelling a distance of 50 cm. through the bath, the yarn is passed into a second bath of acidified water at 90 C. and stretched by 75%. The output of the spinning pump is adjusted to produce, after stretching, filaments of 1.5 denier. The stretched bundle of filaments is washed, wound on a large perforated roller, and dried. It is then formed into skeins, which are desulphurized with a hot sodium sulphate solution and rinsed again, thereafter they are impregnated with an aqueous solution containing 7 g. of formaldehyde and 3.5 g. of ammonium chloride per liter. The skeins are then washed at 80 C. to 85 C.,

which at the same time causes the condensation I and polymerization to take place.

The filaments thus obtained have a swelling value of 55. The tenacity is 2.2 g. per denier in the dry state and 1.2 g. per denier in the wet state, and the elongation at rupture is 14% when dry and 12% when wet.

If these filaments are stretched to breaking point between pairs of rollers 120 mm. apart, and a twist is then applied by a known method, yarns having very good swelling properties are ob tained, which are suitable for the manufacture of stockings and socks, and which have excellent wearing properties and, unlike wool products, undergo no deformation when washed.

Example II To liters of a viscose containing 6% of caustic soda and 8% of cellulose are added 120 cc. of a 50% solution of the product of condensation of adipic acid and glycerin in 6% caustic soda. The mixture is cured to a salt point of 3.0 and spun through a spinneret having 100 holes 0.75 in diameter, into a bath containing 100 to 110 g. of sulphuric acid, 200 to 220 g. of ammonium sulphate and 120 to 130 g. of sodium sulphate per liter, at 45 C. The bristles thus obtained are collected in hydro-extractors and are washed and then formed into skeins. These skeins are subjected to bleaching with a hypochlorite solution containing from 2.0 to 2.5 g. of active chlorine per liter, and having a pH of from 8 to 10, and then to treatment with a bath containing from 1.5 to 2.0 g. of sulphuric acid per liter, thereafter they are thoroughly washed.

The skeins are then immersed in a bath containing 8 g. of formaldehyde and 3.5 g. of ammonium chloride, centrifuged and dried at 80 C. to 85 C. The bristles thus obtained have a swelling value of from to and are of very pale creamy white color. They are suitable for the production of brushes and like articles.

What is claimed is:

1. The process for producing colorless artificial regenerated cellulose filaments with reduced swelling characteristics, which comprises incorporating in a viscose spinning solution, a partly condensed linear polyester of an aliphatic diacid and a polyalcohol which is soluble in dilute soda, spinning said solution into a filament and reacting the spun filament by treatment at C. to C. with not over 10 g. per liter of formaldehyde and an acid catalyst.

2. The process for producing colorless artificial regenerated cellulose filaments with reduced swelling characteristics, which comprises incorporating in a viscose spinning solution, a partly condensed linear polyester of an aliphatic diacid and a polyalcohol which is soluble in dilute soda, spinning said solution into a filament and reacting the spun filament by treatment at 80 C. to 90 C, at a temperature of not over 90 C. with formaldehyde in a concentration of not over 10 g. per liter and an acid catalyst.

3. The process for producing colorless artificial regenerated cellulose filaments with reduced swelling characteristics, which comprises incorporating in a viscose spinning solution, a partly condensed linear polyester of adipic acid and glycerin, spinning said solution into a filament and reacting the spun filament by treatment at 80 C. to 90 C. with not over 10 g. per liter of formaldehyde and an acid catalyst.

4. The process for producing colorless artificial regenerated cellulose filaments with reduced swelling characteristics, which comprises incorporating in a viscose spinning solution, a partly condensed linear polyester of adipic acid and glycol, spinning said solution into a filament and reacting the spun filament by treatment at 80 C. to 90 C. with not over 10 g. per liter of formaldehyde and an acid catalyst.

NICOL AS DRISCH. ANDRE PETITON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,284,839 Paine June 2, 1942 2,303,773 Thackston Dec. 1, 1942 FOREIGN PATENTS Number Country Date 584,217 Great Britain Jan. 9, 1947 

1. THE PROCESS FOR PRODUCING COLORLESS ARTIFICIAL REGENERATED CELLULOSE FILAMENTS WITH REDUCED SWELLING CHARACTERISTICS, WHICH COMPRISES INCORPORATING IN A VISCOSE SPINNING SOLUTION, A PARTLY CONDENSED LINEAR POLYESTER OF AN ALIPHATIC DIACID AND A POLYALCOHOL WHICH IS SOLUBLE IN DILUTE SODA, SPINNING SAID SOLUTION INTO A FILAMENT AND REACTING THE SPUN FILAMENT BY TREATMENT AT 80* C. TO 90* C. WITH NOT OVER 10 G. PER LITER OF FORMALDEHYDE AND AN ACID CATALYST. 